Tandem-Parallel Electrochemical Cells to Produce Hydrogen Peroxide at Reduced Energy Consumption.

Large-scale industrialization of oxygen electroreduction requires producing hydrogen peroxide (H 2 O 2 ) at large yield rates (current density >1 A cm -2 , Faradic efficiency >95%). Under such vigorous reaction conditions, however, serious electric energy consumption (EEC) has been caused. According to the formula ( EEC = Y × 1000 × R × F 2 17 2 × FE 2 ), a linear relationship can be identified between H 2 O 2 yield rates ( Y ) and EEC, and therefore, achieving high yield rates ( Y ) while reducing EEC is very challenging in common electrochemical systems. In this work, we have designed a tandem-parallel oxygen electroreduction system composed of two oxygen electroreduction units. The tandem unit can effectively improve the Faradaic efficiency (FE) while the parallel section reduces total internal resistance ( R ). Consequently, the overall system can achieve a high H 2 O 2 yield rate (592 mg h -1 ) with the lowest EEC (2.41 kWh kg -1 ) ever reported to the best of our knowledge. Further, the tandem-parallel system has shown promising stability by working for more than 10 cycles or 24 h. Besides oxygen electroreduction, other applications have been also demonstrated for the tandem-parallel system that can generate H 2 O 2 for in situ degradation of rhodamine B pollutant.